The present invention relates to a data processing device which is provided with a liquid crystal display and an electroluminescent panel to provide backlighting. More particularly, it relates to a data processing device which automatically turns off the electroluminescent panel if it is left inoperative for a specific period of time and which is provided with a function to indicate to the operator that the panel light has been extinguished.
Conventionally, permeable liquid crystal display devices are developed to improve visibility. Any conventional data processing device incorporating a liquid crystal display normally is provided with an electroluminescent panel for backlighting, the brightness of which is proportional to the applied voltage and frequency. However, the use of a conventional electroluminescent panel at high levels of brightness shortens its service life (the period of time until the luminosity of the electroluminescence fades by one half).